The invention relates to a flexible tube for an endoscope, and more particularly, to an improved flexible tube for an endoscope having antifriction agent distributed between a metallic braided texture and a sheath tube.
A conventional flexible endoscope which is used in the medical field is constructed as illustrated in FIG. 1. Specifically, it includes an operating end 2 which permits a variety of operations to be performed at the proximate end of the endoscope, and a flexible portion 3 of an increased length which is adapted to be inserted into a coeliac cavity of the patient. The operating end 2 is provided with an observation eyepiece assembly 4, a flexure controlling knob 5, an inlet opening 6 through which a treatment instrument such as forceps to treat an affected part is inserted, an instrument riser controlling knob 7, an air ventilation/water feed button 8, a suction button 9 and the like. The operating end is adapted to be connected to a light guide cord 10 which is in turn connected to an illumination light source, not shown. The flexible portion 3 which is adapted to be inserted into a coeliac cavity comprises an elongated freely flexible portion 11, a bendable portion 12 connected in contiguous relationship with the portion 11 to permit a distal end 13 to be directed in any desired orientation in response to an operation of the flexure controlling knob 5, and the distal end 13 contiguous with the bendable portion 12 and which is formed with an aillumination window, an observation window, an outlet opening to permit an access of the treatment instrument into or out of the distal end, air port/water port, all of which are not shown, A number of internal members pass through the flexible portion 11 and the bendable portion 12, including bundles of optical fibres serving as an image guide and a light guide, a tube for containing the treatment instrument therein, air/water supply channel, a wire for operating an instrument riser and the flexure controlling wire and the like. The distal end of these internal members are fixed within the distal end 13.
The bendable portion 12 which forms part of the portion 3 may be by way of example constructed as illustrated in FIG. 2. Specifically, portion 12 comprises a bendable tube 21 in the form of bellows which is formed by a series of articulated metal sleeves of a lesser individual length than portion 12, a metallic braided sheath 23 formed by a meshwork of thin metal wires braided into an annular configuration and applied over the bendable tube 21 so as to surround it, and a sheath tube 22 formed of a material such as rubber or synthetic resin and which is applied over the metallic braided sheath 23. The flexible portion 11 which represents the majority of the portion 3 comprises a helical flex. (see FIG. 7) formed by a helical winding of a band-shaped resilient blade, a metallic braided texture 33 (see FIG. 7) which is formed by a meshwork of thin metal wires braided into an annular configuration, and a sheath tube 32 formed of a material such as rubber or synthetic resin and applied over the braided sheath 33.
An antifriction agent comprising powder of molybdenum disulfide, boron nitride, a talc or the like is distributed between the metallic braided sheath 23 of the bendable portion 12 and its sheath tube 22 as well as between the metallic braided sheath 33 of the flexible portion 11 and its sheath tube 32, by applying it to the outer peripheral surface of the braided sheaths 23, 33 and to the inner peripheral surface of the sheath tubes 22, 32. Such antifriction agents are effective in reducing the degree of friction occurring between the metallic braided sheaths 23, 33 and the sheath tubes 22, 32 when the bendable portion 12 and the flexible portion 11 are flexed, and in preventing damage to the sheath tubes 22, 32 due to abrasion or an increase in the magnitude of force required to flex the bendable portion through the flexure controlling wire 25.
In the conventional construction of the bendable portion 12 and the flexible portion 11, the internal peripheral surface of the sheath tubes 22, 32 is smooth, so that the antifriction agent applied to and distributed between the braided sheaths 23, 33 and the sheath tubes 22, 32 may be scraped off from time to time during the use of the endoscope over a prolonged period of use. Such agent then finds its way into the bending tube 21 and the flex 31 through the meshes of the braided sheath 23, 33 and ultimately fall into the hollow interior of the tube 21 and the flex 31, thus greatly reducing the antifriction effect. This disadvantageously gives rise to a damage of the sheath tubes 22, 32 as a result of the abrasion of the internal surfaces, an increase in the magnitude of force required in operating the bendable and the flexible portion, or a breakage of the flexure controlling wire 25.